This fourth course of the Blockchain specialization provides learners with an understanding of the broader blockchain ecosystem. Learners are introduced to other blockchain platforms, details of two decentralized application use cases, and challenges such as privacy and scalability. They are prepared to discuss permissioned blockchain architectures of Hyperledger and Microsoft Azure's blockchain as a service model and analyze the Augur and Grid+ decentralized application platforms. Course material includes emerging alternative decentralization models such as IPFS and Hashgraph, challenges in broader blockchain adoption, and continuous improvement solutions.